Green Roof Plant Blog

This short-lived perennial, also known as the Hairy Rockcress is a
member of the Brassicaceae or mustard family. Rooted firmly by a
taproot, it will grown anywhere from 8 to 25 inches tall. The stem and
leaves are covered in a fine peach-like fuzz, hence the name hirsuta,
meaning with hair in Latin. Blooming in late spring, usually around
June, Arabis hirsuta has pinkish-cream colored flowers. These flowers
grow in clusters, with four petals each. This plant has a weed-like
tendency, and will sprout after a disturbance. Although this plant
prefers full sun and well-drained soils, it is very stress tolerant and
drought tolerant. The Hairy Rockcress relies mainly in bees, butterflies, moths and other various insects for pollination.

As winter persists, we can only dream of spring-time showers as the high temperatures hover around twenty degrees this week. But one herbaceous perennial is patiently waiting the warmer weather. Also known as the Bird's Foot Violet or Mountain Pansy, this lovely spring violet of the Violaceae family will sure to be braving the weather come spring-time.

Typically blooming anywhere from March to May, this five-petaled violet has two-toned petals, ranging in colors from purples and lilacs to periwinkle hues of blue. They are very popular to the bees and butterflies in the community. They prefer well-drained soils and full sun, but will tolerate partial shade. The Bird's Foot Violet will mature to be about three to six inches tall. Growing best in hardiness zones four through eight, you will most-likely find this little flower in eastern North America.

The nickname Bird's Foot violet stems from the shape of the leaves on this perennial. It will self-seed in optimum growing conditions, but commonly spreads by rhizomes. This creates more of a colony of violets, rather than one or two lone plants.

Mainly known as the American Alumroot, this herbaceous perennial is a part of the Saxifragaceae family. A rosette of basal leaves surrounds the tall stalks that shoot from the center of the plant. These elongated stalks show off yellowish-green flowers, usually blooming in the summer months. This particular plant has no fragrance to it and it also many shades of green. The whole plant is covered in tiny, soft, white hairs.

Very low maintenance, American Alumroot is drought tolerant and likes full sun exposure, but will tolerate a partly shady spot. It grows best in hardiness zones three through nine. Although it depends on mainly breezy conditions for seed dispersal, sometimes bees, hummingbirds and butterflies may lend a helping hand.

Also known as the Dwarf Blazing Star, this herbaceous plant will grow to be anywhere from eight to twenty-four inches tall. The leaves are long and thin; they gradually reduce in size the closer the get to the top of the plant. A handful of spike-like cones then give way to a cluster of showy purple flowers. It blooms regularly from June until September. Bees and butterflies are attracted the the flowers for pollen. It is not uncommon to find rabbits, groundhogs, deer and livestock munching on this perennial.

The Dwarf Blazing Star is a part of the Aster Family (Asteraceae). It is a relatively low maintenance plant, growing best in hardiness zones four through seven. It enjoys full sun exposure and prefers drier conditions. This makes it tolerant of summer heat and drought events, however is also tolerant of humidity. This plant is native to north eastern and central North America. Found frequently in prairies, this wildflower is most abundant following fire events.

Small hairs cover the intertwined stems, shooting off oval leaves and small white flowers. The scientific name, Stellaria media, came about to describe the tiny star-shaped flowers. Mainly a low-growing, matted specimen, this plant makes for some fantastic ground cover. It enjoys full sun exposure, but will also tolerate a partly shaded space.

Chickens are a huge fan of chickweed, which is where this herb has acquired its common name. Although it has many uses, chickweed is still considered a pest in many gardens. Flourishing in various habitats, chickweed can be found in tropical climates such as Hawaii all the way to arctic climates such as Greenland. There is hardly a part of the world in which chickweed has not been found!

Chickweed has been used in a variety of ways for centuries, stretching all the way back to the stone age. Not only is it edible, but also has medicinal uses. All parts of the plant make for great green addition to any salad or sandwich with a light taste similar to that of spinach. Chickweed is an excellent source of many vitamins including A, C & D, along with calcium, iron, zinc, manganese, potassium, phosphorus, silica and copper. Tea is a popular choice of chickweed consumption as well. A finely chopped chickweed can be applied to irritated skin to smooth eczema, cuts, minor burns or rashes.

If found on an extensive green roof, it is rarely invasive and can be tolerated to create more biodiversity. Their shallow root system prevents erosion of the growing media and their short life cycle can add helpful organic components for other perennial plants. If this amazing survivor is not wanted it can be easily hand weeded before it flowers.

Relating to my trip out to California last week, I wanted to pick a plant native to the western coast. Sedum oreganum is a succulent mostly known by the name, Oregon stonecrop. It grows on the coasts of California all the way up to Alaska. Keeping color all year round, this herbaceous plant will sprout star-shaped yellow flowers in the summer attracting lots of insects including bees and butterflies. Only to turn a brilliant burgundy in the fall months. This succulent loves sunshine; the more sun it receives over the summer, the more striking the colors will be in the fall months. It grows best in hardiness zones two through nine and in full sunshine. Very drought tolerant and only growing a few inches tall, it makes for an efficient spreading ground cover.

Also known as Arctic Sage, this member of the Aster family is common in the Rocky Mountains and great plains of North America. Growing to approximately a foot tall, this plant is perfect for erosion control or simply as ground cover. It loves the sunshine and is considered drought tolerant. It is a woody-based perennial with an evergreen color, covered in silvery hairs, giving it an almost frosty appearance. Blooming in the summer months, the pale yellow flowers and fruit are rather discreet.

The arctic sage will spread rapidly in over-grazed lands, making some consider it as a weed. Although it was once valued by the Native Americans as they commonly used it to treat various ailments such as colds, wounds and headaches.

Brilliant magenta flowers bloom in late summer and will last into the early autumn month. Also known as Pink Carpet, this low-growing succulent will spread quickly, creating generous ground cover. A part of the Aizoaceae family, this dwarf perennial plant is native to South Africa. Very drought tolerant and growing only four to five inches tall, it flourished best in hardiness zones six through ten. Preferably planted in more arid climates, Pink Carpet won't tolerate soggy soils. The winter foliage ranges from yellow-green to an orange toned bronze color.

With a slight chill in the air these past weeks, I thought it was time to introduce some plants suitable for green roofs that will happily show their full colors in the autumn months. My first pick is Aster oblongifolium. Also known as the aromatic aster, this herbaceous perennial is native to the Central and Eastern United States. This wildflower enjoys full sun exposure and grows best in hardiness zones three through eight. Typically growing one to two feet tall, this plant will take on a more bush appearance when compared to other aster varieties. Taking the size of this wildflower into consideration, this perennial should be chosen for a semi-intensive rooftop garden.

The blooms can start appearing as early as August and last into November. These showy bluish-purple flowers have an amber colored center which commonly attracts birds, bees and butterflies. When crushed, this plant will give out a pleasant balsam-like scent, hence the name, aromatic aster!

Sedum floriferum is a perennial which serves as a fantastic ground cover. A slightly darker green foliage, the spongy succulent leaves retain water easily, making this sedum drought tolerant. It will grow approximately four to six inches high. Enjoying full sun, this plant will thrive best in hardiness zones three through nine. It will produce bright yellow, star-shaped flowers in late spring or early summer. Little care should be needed for this independent stonecrop. It invites many nectar-attracted species including butterflies and honey bees. This sedum is easily spread by root cuttings.